Early postnatal complications in small-for-gestational-age infants by gestational age and SGA severity

Small-for-gestational-age (SGA) infants commonly experience hematological complications and hypoglycemia. This study investigated how the frequencies of these complications varied according to SGA severity and gestational age. This single-center retrospective cohort study included SGA infants admitted to a neonatal intensive care unit from 2019 to 2020. Infants were categorized by SGA severity (severe or mild) and gestational age (preterm or term). Frequencies of neutropenia, polycythemia, thrombocytopenia, and hypoglycemia were compared using unadjusted analyses. Unadjusted risk ratios with 95% confidence intervals (CIs) were calculated, and exploratory receiver operating characteristic analyses were performed with cutoffs selected by maximizing the Youden index. Among 147 SGA infants (68 severe and 79 mild; 65 preterm and 82 term), neutropenia occurred in 8.2%, polycythemia in 2.7%, thrombocytopenia in 11.6%, and hypoglycemia in 45.6%. In unadjusted comparisons, neutropenia, thrombocytopenia, and hypoglycemia were more frequent among severe than mild SGA infants and among preterm than term SGA infants. Only 4 infants had polycythemia, and no clear association was detected. The area under the receiver operating characteristic curve was 0.86 (95% CI = 0.74–0.97) for neutropenia, 0.74 (95% CI = 0.60–0.88) for thrombocytopenia, and 0.75 (95% CI = 0.67–0.83) for hypoglycemia. The selected cutoffs were ≤34 weeks for neutropenia (sensitivity, 83.3%; specificity, 80.0%) and thrombocytopenia (sensitivity, 58.8%; specificity, 79.2%), and ≤37 weeks for hypoglycemia (sensitivity, 92.5%; specificity, 46.3%). Neutropenia, thrombocytopenia, and hypoglycemia were more frequent among severe SGA and preterm SGA infants in unadjusted comparisons. The gestational-age cutoffs were exploratory findings that require confirmation in larger external cohorts before clinical use.